Communication systems -- Find the Modulation Depth....

[bonildo]

Homework Statement

Hello, the plot in the image shows a modulated signal s(t), with one period of the modulating signal m(t). The mean value of m(t) is equal to zero . Its asked me to find the modulated index, the amplitude of the carrier, the equation of the message(m(t)) and the kind of modulation (DSB-SC or AM).

Homework Equations

s(t)=A*m(t)*cos*2*pi*fc*t) (dsb-sc modulation)
s(t)= (1+ka*m(t))*cos*2*pi*fc*t) (am modulation)

The Attempt at a Solution

I don't know, I'm really stuck in this exercise.

 

[Dr. Courtney]

Have you tried plotting those questions with various values of the constants to help learn their meanings?

 

[bonildo]

Have you tried plotting those questions with various values of the constants to help learn their meanings?

Yes, I do. But I can't still figure out a solution for it.

I tried to solve s(0)= (1+ka*m(0)), but I don't know who is m(t)

 

[NascentOxygen]

the plot in the image shows a modulated signal s(t), with one period of the modulating signal m(t).

The image seems to not show m(t). You are making this difficult for yourself if you ignore the assistance a sketch of the modulating signal will likely give you.

If you are not shown m(t), perhaps you can figure it out, or even "guess" it?

 

[rude man]

Homework Statement

Hello, the plot in the image shows a modulated signal s(t), with one period of the modulating signal m(t). The mean value of m(t) is equal to zero . Its asked me to find the modulated index, the amplitude of the carrier, the equation of the message(m(t)) and the kind of modulation (DSB-SC or AM).

Homework Equations

s(t)=A*m(t)*cos*2*pi*fc*t) (dsb-sc modulation)
s(t)= (1+ka*m(t))*cos*2*pi*fc*t) (am modulation)

The Attempt at a Solution

I don't know, I'm really stuck in this exercise.

I suggest:
take the two s(t) signals in "relevant equations". Take one at a time.
Can you imagine s(t)=A*m(t)*cos*2*pi*fc*t) (dsb-sc modulation) giving you the shown signal?
Can you imagine s(t)= (1+ka*m(t))*cos*2*pi*fc*t) (am modulation) giving you the shown signal?
Only one of those two can give you the shown signal.
And a little thinking should get you the answers you seek.
Hint: only one of your s(t) can produce a signal with differing maxima (5 and 15).
P.S. obviously, m(t) is a sinusoid.